Integrated optical apparatus and associated methods

ABSTRACT

An integrated optical apparatus includes an optically transparent substrate with a light source and a detector mounted adjacent thereto. The substrate includes an optical element in a transmit path from the light source to a remote target. The optical element splits the light into more than one beam. A detector receives beams reflected by the target. All optical elements needed to create the more then one beam, direct the more than one beam onto the target and direct the more than one beam from the target to the detector are on the substrate and/or any structure bonded to the substrate. Preferably, the optical element provides sufficient separation between the more than one beam such that each beam is delivered to a unique respective light detecting element of the detector. The return path from the remote target to the detector may include an optical element for each beam or no optical elements. An additional substrate may be included and bonded to the substrate. The active elements may be bonded to a bottom surface of the substrate, either directly or via spacer blocks, or may be provided on a support substrate, which is then bonded, either directly or via spacer blocks, to the substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.09/274,310 filed Mar. 23, 1999 now U.S. Pat. No. 6,104,690 which is acontinuation of U.S. application Ser. No. 09/018,891, now U.S. Pat. No.5,912,8720, filed on Feb. 5, 1998 which is a continuation-in-partapplication of U.S. application Ser. No. 08/727,837 filed on Sep. 27,1996 entitled “Integrated Optical Head and Associated Methods”, and acontinuation-in-part of U.S. application Ser. No. 08/994,281, now U.S.Pat. No. 5,886,971, filed on Dec. 19, 1997, the entire contents of allof which are hereby incorporated by reference for all purposes.

FILED OF THE INVENTION

The present invention relates to the field of optics and, moreparticularly, to an integrated optical apparatus providing more than onesignal in separate return paths.

BACKGROUND OF THE INVENTION

Many typical computer systems include a disk drive cooperating withstorage media to permit storage and retrieval of data. A typical opticaldisk drive includes an optical head that conventionally uses a laser totransmit light to the optical disk. Light reflected from the surface ofthe disk is detected by an optical detector and processed to read datafrom the disk. An example of such an optical head is disclosed, forexample, in U.S. Pat. No. 5,204,516 titled “Planar Optical Scanning HeadHaving Deficiency Correcting Grating” by Opheij.

The size of the various optical head components, however, are often toolarge for many desired applications and many market demands. Also, asdensities of integrated circuits and system boards increase, the demandfor smaller components increases. Additionally, the production processfor a conventional optical head requires that the laser be excited orturned-on (i.e., “active alignment”) for 25 alignment of the laser, thedetector, and the optical elements. An example of active alignmentprocesses is illustrated and described in an article 10 published inOptical Engineering (June 1989) titled “Holographic Optical Head ForCompact Disk Applications” by Lee.

Unfortunately, these active alignment requirements are complex, timeconsuming, and relatively expensive. Further, the level of sizereduction in the vertical direction of an optical head is limited. Inaddition, the relatively large size of the elements of an optical headwhich can be manipulated is determined by the need for active alignment.

SUMMARY OF THE INVENTION

With the foregoing background in mind, it is therefore an object of thepresent invention to provide an optical head, such as for a disk drive,and related methods which is more compact and less expensive tomanufacture. It is further an object of the present invention to providemore than one signal having unique return paths.

These and other objects, advantages, and features of the presentinvention are provided by an integrated optical head having more thanone or no optical elements in a return path from a target, therebyforming unique return paths for each beam. The integrated optical headpreferably includes an optically transparent substrate having first andsecond faces. The substrate may include a diffractive optical elementformed on a face thereof. A light source, such as a laser, is positionedadjacent the first face of the substrate to transmit light through thesubstrate, through the diffractive optical element, and toward a target,such as optical storage media. An optical element provided in thesubstrate splits the light from the light source into more than onebeam. An optical detector is positioned adjacent the first surface ofthe substrate to detect respective beams reflected from the target andthrough the substrate. All of the optical elements needed to create themore than one beam, direct the more than one beam onto the target, anddirect the more than one beam form the target onto said detector are onthe substrate and/or any structure bonded to the substrate. Preferably,the detector includes more than one detecting element for detectingrespective beams of the more than one beam.

In another embodiment, a second transparent substrate is aligned andjoined to the first substrate. The second substrate may carry one ormore optical elements. According to this aspect of the invention,alignment areas in the form of benches or other mechanical features maybe formed in one surface and mating recesses, for example, may be formedin the other surface. Adhesive attachment areas, which may overlap thealignment areas, hold the substrates together. Alignment may also beaccomplished at the wafer level by having the elements of each dieaccurately placed using photolithography to accurately align the twowafers. The assembled dies can then be diced without the individualalignment means or steps being required for connecting the first andsecond substrates.

These and other objects of the present invention will become morereadily apparent from the detailed description given hereinafter.However, it should be understood that the detailed description andspecific examples are given by way of illustration only and are directedto the preferred embodiments of the present invention, since variouschanges and modifications within the spirit and scope of the inventionwill become apparent to those skilled in the art from this detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

Some of the objects and advantages of the present invention having beenstated, others will become apparent as the description proceeds whentaken in conjunction with the accompanying drawings in which:

FIG 1A is a schematic view of a configuration of an integrated opticalapparatus in accordance with the present invention;

FIG. 1B is a schematic view of another configuration of an integratedoptical apparatus in accordance with the present invention;

FIG. 1C is a schematic view of an integrated optical apparatus accordingto the present invention;

FIG. 2 is a fragmentary side perspective view of an integrated opticalapparatus according to the present invention;

FIG. 3A is a side elevational view of an integrated optical apparatusaccording to the present invention;

FIG. 3B is side elevational view of the integrated optical apparatus asshown in FIG. 3A rotated ninety degrees;

FIG. 4A is a plan view of the component side of a first transparentsubstrate of an integrated optical apparatus according to the presentinvention;

FIG. 4B is a plan view of a holographic optical element of a firsttransparent substrate of an integrated optical apparatus according tothe present invention;

FIG. 4C is a plan view of a refractive lens surface of a secondtransparent substrate of an integrated optical apparatus according tothe present invention;

FIG. 5 is a cross sectional view of an integrated optical apparatus ofthe present invention having a diffractive element in the transmit pathand separate diffractive elements in the return path;

FIG. 6 is a cross sectional view of an integrated optical head of thepresent invention having a diffractive element and a refractive elementon a single substrate in the transmit path and no optical elements inthe return path;

FIG. 7 is a. a cross sectional view of an integrated optical head of thepresent invention having a diffractive element and a refractive elementon two substrates in the transmit path and no optical elements in thereturn path;

FIG. 8 is a vertical sectional view of a substrate showing a method ofcreating a hybrid microlens for an integrated optical head according tothe invention;

FIG. 9 is a perspective view showing an article including two wafersaccording to the present invention; and

FIGS. 10A-10D are vertical fragmentary sectional views of examplealignment features according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theillustrated embodiments set forth herein. Rather, these illustratedembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the invention to thoseskilled in the art. Like numbers refer to like elements throughout.

FIG. 1A is an optical design schematic of an integrated assemblyincluding a light source 10, a transmit diffractive optical element(DOE) 6, a transmit refractive lens 12, a return refractive lens 8 and adetector 17. These elements are integrated onto transparent substrates.Light output by the light source 10 is split into a plurality of lightbeams by the DOE 6. These beams are delivered to a target surface 14 viathe transmit refractive lens 12. In FIG. 1A, two beams 2, 4 are shown asan example, although any number may be used. These beams are reflectedby the target surface to the detector 17 via the return refractive lens8. The detector may include more than one detector, one for each beam,or a single detector with unique areas designated for each beam.

When the light source is a laser, it is preferably the semiconductorlaser chip itself, i.e., not a laser inside a can as typically providedfor a macroscopic system. Since the dimensions of the integrated systemare much smaller than those for a conventional macroscopic system, thelight source must be fairly close to the DOE 6, so that the beam willnot be too large thereon and all of the beam will be received by the DOE6. Thus, part of the integrated approach of the present inventionpreferably includes providing the laser chip or die itself adjacent to atransparent substrate.

In forming an integrated optical apparatus, the first design was toattempt to simply scale down a macroscopic design. In other words, asingle lens was placed in the return path, as shown in FIG. 1A. In amacroscopic configuration, this lens in the return path provides bothseparation to the beams as well as focussing thereof in order toproperly deliver them to the detector.

In the transmit path from the light source to the detector, the lightfrom the light source 10 is delivered to the DOE on the top surface ofthe substrate 11 at a distance from the light source 10. This distanceis used to advantage to provide an adequately wide beam at the DOE. Thebeams formed by the DOE are focused on surface 14 located at a distancefrom the lens 12. This distance is chosen to achieve adequate spot sizemodulation depth and depth of focus at the media surface.

In the return path from the target 14 to the detector 17, the refractivelens 8 is located at a distance d2 from the target and the detector 17is located a distance d1 from the refractive lens 8. The distances d1,d2 are dictated by the substrates 11, 21 on which these elements aremounted. The ratio of the distances d1/d2 determines the amount ofdemagnification of the image reflected from the media that occurs in alens. In using a single lens in the return path, this demagnificationaffects not only spot size but spot spacing. Assuming, for example, aspot size of 0.020 mm on the target 14, a demagnification of ¼ gives aspot size of 0.005 mm which because of aberration is spread to an area0.025 mm. When a single lens in the return path is used, as shown inFIG. 1A, the spacing of the spots is demagnified to 0.025 mm andsignificant crosstalk noise results. This can be seen by the overlappingbeams in the plane of the detector 17 in FIG. 1A. The overlapping of thebeams also occurs at the return refractive lens 8. In order for therefractive lens to image the beams at a point at which they aresufficiently separated such that the beams will be distinguishable onthe detector 17, the return refractive lens 8 would have to be placedcloser to the target 14. However, such positioning would destroy thedesired integrated nature of the optical apparatus.

In this configuration, in order for the return refractive lens 8 toproperly focus the beams, the angles of the beams 2, 4 need to be assmall as possible and as similar as possible, so that these beams mayboth impinge upon a central portion of the return refractive lens 8. Inthe relative scale of FIG. 1A, using the distances from the top surfaceof the top substrates to the target, the angle of beam 2 is 5.6 degreesand the angle of beam 4 is 6.9 degrees. However, the beams 2, 4 alsoneed to be sufficiently separated on the detector 17. These two designconstraints cannot be met using the single refractive lens 8 forreceiving all of the beams in the return path while providing anintegrated optical apparatus.

FIG. 1B is an alternative configuration created by recognizing that byproviding larger angles to the light beams and providing greaterdifference between the angles of the light beams, the need for anoptical element in the return path could be eliminated. In other words,the separation between the light beams 2,4 in FIG. 1B is sufficient suchthat the beams remain separate and distinguishable on the detector 17without requiring an optical element in the return path to provide thisseparation. In FIG. 1B, the angle of beam 2 is 8 degrees and the angleof beam 4 is 11 degrees.

In FIG. 1B, the distance between the top surfaces of the top substratesand the target 14 is the same as it was in FIG. 1A. This clearly resultsin the beams being further separated on the target 14. For manyapplications, this increased separation is not a problem, but for thosefor which a particular separation is desired, the integrated opticalhead can be positioned closer to the target 14.

While the configuration shown in FIG. 1B is advantageous for integratedapparatuses, for many applications, the complete elimination of opticalelements in the return path results in an unacceptable level of noise. Asolution, an example of which is shown in FIG. 1C is to include separateoptical elements for each beam in the return path. The ability to usemore than one optical element in the return path can be realized due tothe increased separation between the beams. The feasibility of such asolution, requiring more than one optical element for each beam, isfacilitated by the passive alignment discussed in detail below.

FIG. 1C is an optical design schematic of an assembly according to theinvention for use in, for example, detecting an optical track on astorage media. A light source 10 directs coherent light, with adispersion angle of fifteen degrees, upward through an object distanced1 through a diffractive element (DOE) not shown and to a refractivelens 12. The DOE divides the light into a number of beams, only three ofwhich are shown as a plurality of rays in FIG. 1C. The beams are focusedon surface 14 located at an image distance from the lens 12. The spotsize and spacing of the light on the image surface 14 determines thetracking accuracy and therefore the amount of information that can bestored on the media. The size to which the spot can be reduced is in theinstant design, approximately 0.020 mm. In the design of FIG. 1, therefractive lens 12 must have a significant curvature in order to focusthe light to 0.020 mm spots on the media. The spots of light are spacedapproximately 0.100 mm from each other on the media to limit crosstalknoise. As would be readily understood by those skilled in the art theoptical head can be positioned by the illustrated positioning means 29.

Preferably, all optical elements needed to create the more than onebeam, direct the beams onto the target and direct the beams from thetarget to the detector are on the substrate and/or any structure bondedthereto, thereby providing an integrated optical apparatus. Preferably,any optical elements in both the return path and the transmit path areless than 500 microns in diameter, more preferably, less than 300microns in diameter. The actual size of the elements will be dictated bythe overall size of the device with which the integrated opticalapparatus is to be used, with a lower practical limit being on the orderof a wavelength.

If a design were attempted using a single lens as taught in the priorart where the elements are not integrated, the lens curvature requiredto focus the laser light to 0.020 mm spots in this compact architecturewould control the dimensions of the single lens. Thus the use of asingle lens as taught in the prior art for reducing the size of opticalheads, is a limiting factor in size reduction of the entire optical headassembly. This factor is one of the reasons that multiple lenses areemployed in the instant invention instead of a single lens. The use ofmultiple lenses is enabled by having the separation between the beams besufficient so that each beam is incident only on one of the lenses inthe return path.

The ratio of the distances d1/d2 determines the amount ofdemagnification of the image reflected from the media that occurs in alens. In a single lens design, this demagnification affects not onlyspot size but spot spacing. A demagnification of ¼ gives a spot size of0.005 mm which because of aberration is spread to an area 0.025 mm. If asingle lens design had been used, the spacing of the spots would alsohave been demagnified to 0.025 mm and significant crosstalk noise wouldresult. By using individual lenses, spaced approximately 0.200 mm, thedetectors can be spaced at about 0.220 mm and thereby eliminatecrosstalk noise using the 0.025 mm light spots.

Thus, by providing increased separation to the beams in the transmitpath, separate optical elements for each beam's return path may be used,thus allowing proper focussing of the beams on the detector. Further,such separate elements are more readily integrated into a compactsystem. In an integrated system, it is advantageous to place the gratingon the media as close to the light source as possible, but separationbetween the beams needs to be maintained. If the distance is too small,in order to maintain the separation, a bigger angular deflection isrequired. Then the beams are more spread out and the system will becometoo large in the x-y direction (with z being in the plane of the paper).This spread also increases the aberrations. Therefore, the angles needto be as small as possible, while maintaining separation even over thesmall distance from the light source and to the detector.

FIG. 2 is a side view of a magnetic floppy disk head 5 with an opticaltracking assembly according to a preferred embodiment of the invention.Head 5 is mounted, in arm 3 by known means not shown, for the extensionacross the various tracks of media 14. Head 5 is electrically connectedto read and write circuits and tracing control circuits by a flexibleprinted circuit 7. A recess 9 of approximately two millimeters by onepoint six millimeters and four and a half or five millimeters deep isprovided in head 5 in which the optical assembly comprising substrate 11is mounted and connected to flexible printed circuit 7. It will beappreciated that the same assembly techniques and methods of theinvention may be used to assemble optical disk read heads, as well asmagnetic disk heads with optical tracking.

Referring now to FIG. 3, a first transparent substrate 11 comprisingfused silica or other optical material has component mounting metalizedpads or contact pads placed on its bottom surface 13, such as usingsubstrate fiducial marks or indicia and accurately alignedphotolithographic masks and metal deposition steps known in the art ofmicroelectronic circuit manufacture. In this preferred embodiment,surface 13 of substrate 11 is approximately 1.6 mm by 2 mm and thesubstrate 11 is approximately 0.8 mm thick. A laser chip 15 is mountedto the surface 13 by means of some of the mentioned metalized pads. Asshown in FIG. 4, laser 15 is an edge emitting laser with the laser lightdirected upwards through means of a precision mirror 33 as shown in FIG.4. It will by understood that the edge emitting laser 15 can be replacedwith a vertical cavity surface emitting laser and thereby obviate theneed for the precision mirror in order to direct the laser beam normalto the substrate surface.

An optical detector chip 17 is also mounted to the component surface ofsubstrate 11 by means of the metalized pads. A hologram surface 19 onthe opposite side of substrate 11 carries the diffractive opticalelements shown in detail in FIG. 7. The diffractive optical elementphase profiles are designed using the computer calculations andmanufactured using techniques taught by Swanson et al. in U.S. Pat. No.5,161,059, the entire disclosure of which is incorporated herein byreference.

The optical elements are created photolithographically using the samefiducial marks or indicia used to place the metalized pads. Alternatelysecond fiducial marks that have been aligned with the first marks may beused to align the masks that are also used to create the opticalelements. In this way, when the light source, mirror and detector aremounted on their metalized pads, the optical paths among the devices andthrough the optical elements are in optical alignment as shown moreclearly in FIGS. 3A and 3B. The precision mirror, if needed forredirecting light from an edge emitting laser, is considered to be adevice for the purposes of this description only because of the way itis mounted using metalized pads and solder as a silicon chip would bemounted. The hologram surface 19 also has the attachment areas 23 thatattach the first transparent substrate 11 with a second transparentsubstrate 21.

The second substrate 21 carries the refractive optics in a surface 25that provides the second lens of lens pairs or doublets. Light fromlaser 15 is shaped and split by a diffractive optical element inhologram surface 19 into five separate beams of light that are directedthrough substrate and travel approximately 2.4 mm to the media. Only thechief ray of each beam is shown in FIG. 3 for clarity of thedescription. One beam is used for intensity feedback to control theelectrical power to laser 15. The other four beams are used for mediaposition or tracking detection. The beams of coherent light arereflected from media 14 and return through second substrate 21 and firstsubstrate 11 to be detected by detector 17. Since the elements are allin their designed optical alignment by virtue of the placement of themetalization pads, there is no need to energize the laser and move theelements relative to each other to bring them into optical alignment. Inother words, passive alignment is used rather than the active alignmentrequiring operation of the laser as in the prior art. It will berecognized that although the beams preferably pass first through thediffractive optical element in surface 19, the order of the opticalelements in the light path could be changed or the elements could becombined into one more complex element without departing from the scopeof the invention.

FIG. 3B is another side view of the assembly of FIG. 3A. As shown inFIG. 3B, the light emitted by edge emitting laser 15 comes outsubstantially parallel to the plane of component surface 13 and must bedirected normal to the component surface by the 45 degree surface ofmirror 33. The light can then pass through substrate 11, a diffractiveoptical element in surface 19, a refractive lens 61 in surface 25,substrate 21 and be reflected from media 14 as shown in FIGS. 1A-1C and3A.

FIG. 4A is a plan top view of the component surface 13 looking downthrough transparent substrate 11. Electrical contact metalizations 39,41, 43 and 45 provide electrical connections to detecting photo-diodesin detector 17. Centered under detector 17 is a metalized area 53 havingthree apertures through which light reflected from media 14 is received.Solder ball alignment areas 47 on each side of area 53 serve both aselectrical contacts and as alignment mechanisms in this embodiment. Theareas 49 are also solder balls or pads which serve to align and connectthe laser 15 to the first substrate and provide current to laser 15.Areas 51 on the other hand only provide mechanical alignment andmechanical attachment of mirror 33 to first transparent substrate 11.

The hologram surface 19 appears in FIG. 4B in plan view, again lookingdown onto substrate 11. Hologram surface 19 has metalized area 55 whichacts as a mask to reduce stray light but allow three beams created bydiffractive optics from the light from laser to be directed to media 14from which they are reflected to reach detector 17 through the fiveapertures shown in metalized areas 59. Surrounding metalized area 55 isa diffraction grating 57 that scatters stray light from laser 15 so thatit does not adversely affect detector 17.

FIG. 4C shows the refractive lens surface 25, again in plan view lookingdown, this time through substrate 21. Lens 61 in combination with thediffractive optical elements in mask 55 shape and focus the laser lightinto three spots of approximately 20 Am diameter and spaced atapproximately 100 microns onto media 14. Lenses 63 and 65 focus thelight reflected from media 14 through mask 59 to detector 17 forposition control and/or reading. Lens 67 focuses reflected light to thephoto-diode of detector 17 that provides an intensity level signal tothe power control circuits which control the electrical power providedto laser 15. Surrounding both surface 19 and surface 25 is an attachmentarea shown generally as area 71 in FIGS. 4B and 4C. Area 71 containsspacing stand off benches and is the area in which an adhesive is placedin order to join substrate 21. The standoff benches passively define aproper or desired vertical spacing or alignment. Preferably the adhesiveis ultraviolet light cured adhesive that can be laid down withoutconcern for time to harden. The adhesive is placed in areas 71 and thenafter the substrates 11 and 21 are aligned, the assembly is flooded withultra-violet light to catalyze the adhesive. In an alternate embodiment,the adhesive is replaced with photolithographically placed metalizationpads and the two substrates are joined using solder ball technology.

FIG. 4B also shows three diffractive optical elements 73, 75 with mask55. These three elements 35 provide the five beams of light to bereflected from the media, the three main rays of which are shown in FIG.3A. Element 75 provides the power control beam that is reflected fromthe media and is received at aperture 79 in mask 59 as shown in FIG. 8.Elements 73 and 77 each provide two beams that interfere at the mediasurface to create a dark band with two light bands on either side of thedark bands. The light bands are reflected back down to the pairs ofapertures 81, 83 and 85, 87 shown in FIG. 4C to provide the varyinglight intensity that is used to detect an optical track on the media.The apertures 73, 75 and 77 containing diffractive elements are eachapproximately 100 microns long and 20 microns wide.

FIG. 5 illustrates an alternative to providing separate refractiveelements in each return path. In FIG. 5, each refractive element in thereturn path has been replaced with a diffractive element 39. Therefractive element in the transmit path has also been replaced with adiffractive element 37 for splitting radiation output by the radiationsource 15, and delivered to the diffractive element 37 via the precisionmirror 33. The diffractive element 37 provides separation to the beamsdelivered to the grating on the surface 14. The use of diffractiveelements in the return path is typically not as advantageous asrefractive elements. The diffractive elements are more wavelengthdependent and less efficient for larger angles.

Also in FIG. 5, as well as FIGS. 6-7, the active elements are mounted ona support substrate 31, preferably a silicon substrate. This supportsubstrate 31 also serves as a heat sink for the active elements mountedthereon. Attachment areas 23 separate the substrate 31 from thesubstrate 11 on which the diffractive elements 37, 39 are mounted. Theactive elements may be mounted support substrate 31 using passivealignment in a similar manner as discussed above regarding the mountingof these elements on the transparent substrate 11. The attachment areas23 can be provided by etching a recess into the support substrate 31 inwhich the laser 15, the detector 17, and the optional mirror 33 may beprovided. In other words, the unetched portions of the substrate 31serve as attachment areas 23. The substrates 11, 31 may then be bondedwith solder material 27. Further, an angled sidewall of the substrateadjacent the recess therein can serve as the mirror 33. Alternately, theattachment areas 23 may include spacer block separate from the substrate31, as shown in FIGS. 6 and 7. The mirror 33 can be a separate elementfrom the spacer blocks, as shown in FIG. 6 or can itself serve as aspacer block, as shown in FIG. 7.

As shown in FIG. 6, another embodiment of the present invention isdirected to employing no optical elements in the return path. Thediffractive element 37 in the transmit path is designed to providesufficient spread to the radiation such that the beams incident on thedetector 17 are still distinguishable. This is facilitated by theprovision of a refractive element 19 on an opposite surface of thesubstrate 11 from the diffractive element.

FIG. 7 illustrates yet another embodiment in which no optical elementsare used in the transmit path. In FIG. 7, the refractive element 19 ismounted opposite the diffractive element 37 on a further substrate 21.

Referring now to FIG. 8, a method of photolithographically placing anoptical element on a substrate surface 25 in alignment with diffractiveelements and/or electrical devices is shown. A refractive opticalelement in the form of a microlens 115 is formed by placing a circularlayer of photoresist 111 on a surface of optical material using a mask.The photoresist is then partially flowed using controlled heat so thatthe photoresist assumes a partially spherical shape 113. Thereafter, thesurface 25 is etched and a refractive element 115 having substantiallythe same shape as the photoresist 113 is formed by the variable etchrate of the continuously varying thickness of the photoresist 113. Inthe event that a hybrid optical element is desired, the microlens 115 isfurther processed by etching or embossing steps. In one embodiment, alayer of photoresist 117 is placed over the microlens 115 and exposedthrough a photolithographic mask with the phase pattern of a diffractiveoptical element. When the exposed photoresist is then developed, thesurface of the microlens can be further etched with the diffractiveoptical element pattern to produce a hybrid optical element 119. Inanother embodiment, a polymer is placed over the microlens in place ofthe photoresist and the phase pattern is embossed into the polymer asshown at 121. It also will be understood that although a convex elementhas been shown, the same technique can be used to create a concavemicrolens. The single surface hybrid element 119 is preferably used inthe transmit path, for example, in place of the two surface hybridelement shown in FIG. 6.

In the structures of all of the figures discussed throughout having morethan one substrate, all of the substrates may be passively aligned andattached using patterns formed photolithographically as discussed below.While the following discussion references the transparent substrates 11,21, the support substrate 31 may also be aligned in an analogousfashion. When aligning the support substrate containing active elements,the integrated optical apparatuses shown in FIGS. 5-7 may be formed bypassively aligning a support wafer having a plurality of active elementsthereon with a transparent wafer having a corresponding plurality ofoptical elements. This support-transparent wafer pair may then be dicedapart. Alternatively, the support wafer can be diced and individuallaser/detector assemblies aligned and attached to the transparent wafersuch as by flip-chip attachment. By first forming individual activeassemblies, the lasers can be tested separately.

FIG. 9 shows the two transparent substrates 11 and 21 prior to theirbeing assembled into optical assemblies and diced. Because each elementhas been accurately placed on each substrate using photolithography, theentire wafers can be aligned and joined prior to being diced into chipswithout the need to energize any of the laser devices on the substrate11. FIG. 9 shows the substrates inverted from the way they are shown inFIGS. 2, 3A and 3B in order to show the lasers, mirrors and detectors inplace on top of each die. Of course, if the support substrate 31 beingaligned with one or both of the transparent substrates, to form theconfigurations shown in FIGS. 5-7, these active elements are not on thetop of the wafer 11.

Prior to putting the wafers together, the adhesive material, e.g.,ultra-violet curable solder, is placed in the area 71 of each die on atleast one of the wafers. After the adhesive is placed, the two wafersare placed one above the other and aligned. In one embodiment of theinvention, a known photolithographic mask aligning tool is used withvernier fiduciary marks 93 and 95 to monitor the relative displacementof the two substrates until they are in alignment with each other. Thesubstrate 11 can then be lowered onto substrate 21, thealignment—rechecked, and the adhesive catalyzed by ultraviolet light.

In another embodiment, the two wafers are passively aligned usingmechanical mating elements 91. Three forms of mechanical matingelements, in addition to the spacer block previously discussed, arecontemplated and shown in FIGS. 10A, 10B and 10C. One, shown in FIG.10A, takes the form of V-shaped grooves 97 etched into matching faces ofthe substrates 11 and 21. These grooves are then aligned with sphere 99to index the two wafers into alignment. Note that only a few grooves andspheres are needed to align all of the dies while they are stilltogether as a wafer. Another embodiment of the alignment means, shown inFIG. 10B, comprises photolithographically placed metalization pads 101which are then connected by reflowing a solder ball 103. Alternatively,the metalization pads 101 may be solder, without the need for the solderball 103. In a still further embodiment of FIG. 10C, a bench 105 israised by etching the surrounding surface and the bench 105 is indexedinto a recess 107, also created by photolithographically placed etchant,preferably reactive ion etchant.

In the adhesive area 71 of each die, means may be needed to accuratelyspace the two substrates from each other. Spacing is accomplished in oneembodiment by means of a bench 109 shown in FIG. 10D. Three or morebenches 109 are located in the area 71 around each die in an adhesivewith high compressive. In another embodiment, the solder bumps or ballsand metalizations are used in area 23 accomplishing both attachment andalignment as shown in FIG. 10B. Alternately, when an adhesive with highcompressive strength is chosen, only three or more such benches areneeded for spacing the entire wafers and after the adhesive has set, thejoined wafers can be diced without substrate spacing.

Having described the invention in terms of preferred embodimentsthereof, it will be recognized by those skilled in the art of opticalsystem design that various further changes in the structure and detailof the implementations described can be made without departing from isthe spirit and scope of the invention. By way of example, thediffractive optical elements may be placed on the same surface of asubstrate on which the electronic components are accurately placed withthese diffractive optical elements using photolithography. Likewiserefractive optical elements may be placed using photolithography inalignment on the other surface of the same substrate thereby allowing anentire optical assembly to be fabricated using but one substrate withoutthe need for actively energizing a light source in the assembly toaccomplish alignment.

In the drawings and specification, there have been disclosed illustratedpreferred embodiments of the invention, and although specific terms areemployed, the terms are used in a descriptive sense only and not forpurposes of limitation. The invention has been described in considerabledetail with specific reference to these illustrated embodiments. It willbe apparent, however, that various modifications and changes can be madewithin the spirit and scope of the invention as described in theforegoing specification and as defined in the appended claims.

What is claimed is:
 1. An integrated optical apparatus comprising: afirst substrate being optically transparent and having first and secondopposing faces; a divider on said first substrate receiving an inputbeam, outputting at least two beams and directed said at least two beamsto a surface separate from the integrated optical apparatus; and adetector receiving at least one of said at least two beams from thesurface, wherein all optical elements needed to create said at least twobeams, direct said at least two beams onto the surface, and direct saidat least one of said at least two beams from the surface onto saiddetector are on at least one of said first substrate and any structurebonded to said first substrate; and mechanical mating means forpassively aligning said detector to said first substrate.
 2. Theapparatus according to claim 1, wherein said detector includes at leasttwo light detecting elements for receiving a respective beam of said atleast two beams reflected from the surface, wherein said dividerprovides sufficient separation between said at least two beams such thateach beam of said at least two beams delivered to said detector isdelivered to a unique respective light detecting element of said atleast two light detecting elements.
 3. The apparatus according to claim2, wherein said light detecting elements comprises more than one area ona single detector.
 4. The apparatus according to claim 1, wherein saidall optical elements include elements providing focusing to said atleast one of said at least two beams onto said detector.
 5. Theapparatus according to claim 1, further comprising: a support substrate,wherein said detector is mounted on said support substrate; and meansfor bonding said support substrate and said first substrate together. 6.The apparatus according to claim 5, wherein said means for bondingincludes spacer blocks between said first substrate and said supportsubstrate.
 7. The apparatus of claim 1, wherein said mechanical matingmeans includes spacer blocks for providing a precise separation betweenthe detector and the first substrate.
 8. The apparatus according toclaim 1, wherein said first substrate further comprises at least onmetal pad on a bottom face of the substrate used to assist inpositioning said detector.
 9. The apparatus according to claim 8,further comprising a solder pad on top of said at least one metal pad.10. The apparatus according to claim 1, wherein said any structurebonded to said first substrate comprises: a second substrate beingoptically transparent and having optical elements integrated thereon;and means for bonding said second substrate and said first substratetogether.
 11. The apparatus according to claim 10, wherein said meansfor bonding includes spacer blocks between said first substrate and saidsecond substrate.
 12. The apparatus according to claim 1, wherein saiddivider is a single diffractive optical element.
 13. The apparatusaccording to claim 1, wherein said divider includes a plurality ofdiffractive optical elements.
 14. The apparatus according to claim 1,wherein optical elements directing said at least one of said at leasttwo beams from the surface onto the detector are separate from opticalelements needed to create said at least two beams.
 15. The apparatusaccording to claim 1, wherein optical elements needed to create said atleast two beams and direct said at least two beams onto the surface area single optical element.
 16. The apparatus according to claim 1,wherein said all optical elements are in an optical path before said atleast two beams impinge on the surface.
 17. A method for integrating anoptical apparatus comprising: providing a divider on a first substrate,said first substrate being optically transparent, the divider receivingan light, dividing the light into at least two beams and directing saidat least two beams to a surface; mounting a detector adjacent to thefirst substrate, the detector receiving at least one of said at leasttwo beams from the surface separate from the integrated opticalapparatus; and providing all optical elements needed to create the atleast two beams, direct the at least two beams onto the surface, anddirect the at least one of the at least two beams from the surface ontothe detector are on at least one of the first substrate and anystructure bonded to the first substrate, said providing includingpassively aligning the detector with the first substrate.
 18. The methodaccording to claim 17, further comprising: mounting the detector on asupport substrate; and bonding the support substrate and the firstsubstrate together.
 19. The method according to claim 17, furthercomprising bonding a second substrate and the first substrate together,the second substrate being optically transparent and having opticalelements thereon.
 20. The method according to claim 17, furthercomprising precisely separating the detector and the first substrate viaspacer blocks.
 21. The method according to claim 17, further comprisingproviding at least one metal pad on a bottom face of the first substratefor assisting in positioning of the detector.
 22. The method accordingto claim 21, further comprising providing a solder pad on the at leastone metal pad.
 23. The method of claim 17, wherein the first substrateis a wafer, said detector is mounted on a wafer level and then aresultant structure is diced to form a plurality of integrated opticalapparatuses.
 24. An integrated optical apparatus comprising: a firstsubstrate being optically transparent and having first and secondopposing faces; a divider on said first substrate receiving an inputbeam, outputting at least two beams and directed said at least two beamsto a surface separate from the integrated optical apparatus; and adetector receiving at lest one of said at least two beams from thesurface, wherein all optical elements needed to create said at least twobeams, direct said at least two beams onto the surface, and direct saidat least one of said at least two beams from the surface onto saiddetector are on at least one of said first substrate and any structurebonded to said first substrate, wherein said first substrate furtherinclude at least one metal pad on a bottom surface used to assist inpositioning said detector.
 25. An integrated optical apparatuscomprising: a first substrate being optically transparent and havingfirst and second opposing faces; a divider on said first substratereceiving an input beam, outputting at least two beams and directed saidat least two beams to a surface separate from the integrated opticalapparatus, wherein optical elements needed to create said at least twobeams and direct said at least two beams onto the surface are a singleoptical element; and a detector receiving at least one of said at leasttwo beams from the surface, wherein all optical elements needed tocreate said at least two beams, direct said at least two beams onto thesurface, and direct said at least one of said at least two beams fromthe surface onto said detector are on at least one of said firstsubstrate and any structure bonded to said first substrate.
 26. Anintegrated optical apparatus comprising: a first substrate beingoptically transparent and having first and second opposing faces; adivider on said first substrate receiving an input beam, outputting atleast two beams and directed said at least two beams to a surfaceseparate from the integrated optical apparatus, wherein optical elementsneeded to create said at least two beams and direct said at least twobeams onto the surface are a single optical element; and a detectorreceiving at least one of said at least two beams from the surface,wherein all optical elements needed to create said at least two beams,direct said at least two beams onto the surface, and direct said atleast one of said at least two beams from the surface onto said detectorare on at least one of said first substrate and any structure bonded tosaid first substrate, wherein said all optical elements are in anoptical path before said at least two beams impinge on the surface.